Vacuum

The vacuum system at MAX IV will use a different approach in the large 3 GeV ring. The main reason is the small aperture in the magnet gaps, which provides a low-vacuum conductance. The MAX IV vacuum chambers will have a circular copper pipe (outer diameter of 24 mm) which is NEG-coated on the inside to allow for distributed pumping. A cooling channel is added on the outside of the vacuum chamber, in order to handle the synchrotron radiation from dipoles. This way, lumped absorbers are avoided and fewer pumps are required. The experience with the prototype chambers installed in MAX II has been very good.